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The present invention relates to methods for preventing the establishment of an electrical connection between a plug and a socket. More particularly, the present invention relates to lock out devices for use with pin-and-sleeve connectors.
Pin-and-sleeve types of electrical connectors have been developed for a variety of special applications and have proven to be extremely useful and advantageous for a number of reasons. The descriptive name for this type of connector is derived from the construction of the male and female connector portion wherein the electrical contacts in the male part, or plug, are two or more cylindrical, solid, electrically conductive pins which are mounted in the body of the plug and the contacts in the female part, or receptacle, are a corresponding number of electrically conductive sleeves. The pins and the plug are surrounded by a substantially cylindrical protective shroud. The receptacle portion of such connector includes a generally cylindrical insulating inner body having tubular recesses with the elongated conductive sleeves to receive the pins and a shell which is spaced from the insulating body, leaving an annular gap to receive the shroud. The shroud and shell are provided, respectively, with a key and slot so that the orientation of the shroud with respect to the shell, and with respect to the pin-receiving body of the receptacle is easily established.
Additionally, the ground portion of plug portion of the connector is always larger in diameter than the other pins and the conductive sleeve to receive the ground pin in the receptacle body not only is suitably sized to receive the pin but also reaches further toward the open end of the body than the conductive sleeves adapted to receive the other pins, thereby permitting a ground connection to be established before any other connection is made.
Pin-and-sleeve connectors have numerous advantages including the fact that the pin arrangements can be made in a variety of configurations, each configuration being unique to a particular set of voltage, phase and current characteristics. The shroud, as mentioned above, protects the pins from damage and protects the user from accidental contact with the pins. Normally, the receptacle carries the power which is supplied to the plug. Thus, the shroud enters the annular cavity and the receptacle before power is provided to the pins, providing a further safety measure. The shroud construction tends to exclude foreign materials and the overall construction has been found to be highly durable and reliable.
A persistent problem associated with the use of such pin-and-sleeve connectors is that these connectors are often used in very large-scale industrial applications. As a result, an extraordinary length of electrical line can extend from the source of electricity to the device that utilizes the electricity. Often, workmen must work on machines, motors and other electrical devices a considerable distance from the actual plug connections. Under certain circumstances, workers will see that a plug has not been connected into the receptacle and attempt to correct this problem. Persons at the work site may be unaware of the fact that the machine or motor at the other end of the electrical line is being repaired. As a result, the electrician can often suffer a fatal shock from this plugging of the plug into the socket. As such, it is important to prevent such inadvertent connections of the plug into the receptacle. Conventionally, devices that are used to prevent accidental connections between a plug and a socket are called xe2x80x9clock outxe2x80x9d devices. These types of devices are described in various U.S. patents. For example, U.S. Pat. No. 6,220,885, issued on Apr. 24, 2001 to Lemberger, describes a safety locking system including slide bolts for preventing accidental connection.
U.S. Pat. No. 4,957,446, issued on Sep. 18, 1990 to R. R. Belsky, describes a lock out device which includes a securing means which prevents the removal of prongs from the housing so as to prevent unrestricted use of the electrical plug. U.S. Pat. No. 5,281,162, issued on Jan. 25, 1994 to N. E. Ursich, describes a self-locking female receptacle for an electrical cord. U.S. Pat. No. 5,073,122, issued on Dec. 17, 1991 to R. A. Burke, Jr., describes a lock-out enclosure for power connectors. The enclosure is moveable along the electrical line to a position enclosing the power connector. U.S. Pat. No. 5,055,057, issued on Oct. 8, 1991 to P. L. Boyer, describes a locking device for attachment to the male electrical plug of a power supply. None of these prior art patents are particularly adapted for use in conjunction with the pin-and-sleeve types of connectors.
It is an object of the present invention to provide a lock out device which prevents the inadvertent connection of the plug into the receptacle.
It is another object of the present invention to provide a lock out device which effectively prevents electrical shock injuries to workers located at a distance from the power receptacle.
It is a further object of the present invention to provide a lock out device that can be easily applied to a plug of a pin-and-sleeve connector.
It is a further object of the present invention to provide a lock out device which is easy to use, relatively inexpensive and easy to manufacture.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a lock out apparatus comprising a plug having an electrical line extending therefrom and a tubular nose portion, a tubular body having an interior passageway and an exterior surface in which the interior passageway removably receives the nose portion of the plug therein, and a set screw extending through a wall of the tubular body and rotatably movable between a first position exerting a compressive force against the nose portion and a second position releasing the nose portion.
The tubular has a threaded hole formed through a wall thereof The set screw is threadedly received within this threaded hole. The set screw has a surface extending outwardly of the exterior surface of the tubular body. An arm is pivotally connected to this surface of the set screw. The arm is movable to a first position preventing rotational movement of the set screw and to a second position allowing rotational movement of the set screw. A post is affixed to the tubular body and extends outwardly of the exterior surface of the tubular body. The post has a slot formed therein. This slot receives the arm in the first position. The post has a hole extending therethrough on opposite sides of the slot. The arm has an aperture formed therein which is coincident with the hole of the post when the arm is in the first position. A rigid member extends through the hole of the post and the aperture of the arm. In the preferred embodiment of the present invention, the rigid member is a padlock.
The present invention is also a method of preventing a connection between a plug and a an electricity-providing receptacle including the steps of forming a tubular body having an interior passageway slightly larger than the exterior diameter of the nose portion; (2) sliding the tubular body over the nose portion such that the nose portion resides within the interior passageway; and (3) rotating the set screw such that a surface of the set screw compressively contacts the nose portion of the plug.
In the method of the present invention, there is also provided the step of pivoting an arm extending outwardly of the set screw downwardly so that a portion of the arm resides within the slot of the post. The aperture of the arm is aligned with the holes in the post, and then a rigid member to is inserted through the hole and the aperture. The present invention also includes the steps of inserting a ring of the padlock through the hole and the aperture, and then locking the ring into the body of the padlock.